JPH0980276A - Optical fiber cord - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a structure of an optical fiber cord suitable for a reduction in diameter and an economy. SOLUTION: The outer circumference of a communication optical fiber element wire in which an optical fiber is coated with an ultraviolet curable resin or the like is covered with FRP. The outer diameter is 250 μm to 270 μm, and the outer diameter of the strand coated with a UV curable resin is 1
The thickness is preferably 60 μm to 180 μm. Also,
It is desirable that the reinforcing fiber of FRP is glass fiber or aramid fiber. Furthermore, the tensile elastic modulus of FRP is 180
0 kgf / mm ² or is desirably 14000kgf / mm ^2. Bending rigidity value is 0.5 kgf ・ mm ^{2 to} 2.0 kgf ・ mm
² is desirable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to optical communication,
The present invention relates to a structure of a reinforced optical fiber cord used for an optical wiring in a communication device or an optical wiring between devices.

Since the surface of an optical fiber, if left bare, is damaged and easily breaks, the optical fiber is processed and treated into the shape of an elemental wire or a core wire coated with an ultraviolet curable resin, a silicone resin, nylon or the like. Since the coating of the wires or cores is a relatively soft polymer material, when tension is applied to the wires, the internal optical fiber bears most of the tension. Therefore, the strength is weak if it is bare or core wire,
It cannot be used for connection between devices.

As shown in the cross-sectional structure of FIG. 1, a conventional optical fiber cord is made of PVC or the like with a wire 11 or a core wire 11 coated with the optical fiber 1 and a tensile strength fiber 12 such as aramid fiber. It has a structure housed in a pipe or tube 13. In this structure, the tension applied to the optical fiber cord is designed to be borne by the tensile strength fiber.

[0004]

A conventional optical fiber cord has a structure in which a tensile strength fiber is added and a structure in which the tensile strength fiber is gently bundled and housed in a jacket tube in order to ensure the flexibility of the cord. ing. Therefore, the space occupied in the cross section of the optical fiber cord is considerably large, for example, the outer diameter 2
With a fiber optic cord of mm, the cross-sectional area of the air gap is as high as 63%. Therefore, the optical fiber cord has to be thick.

Further, since the tensile strength fibers are gently bundled, a phenomenon occurs in which the tensile strength fibers are effectively loosened by about 0.3% with respect to the optical fiber core when the tensile strength fibers are stored in the outer tube.
This slack means that when tension is applied to the optical fiber cord, the tensile strength fiber does not bear the tension with respect to the initial elongation of 0.3%. For example, the elongation strain allowable for the fiber core wire is 0. When set to 5%, the strain of the tensile strength fiber at the permissible elongation is less by the amount of slack, resulting in 0.2%.
become.

Therefore, it is necessary to increase the amount of tensile strength fiber required to realize the required tensile strength in consideration of this slack. This not only causes the optical fiber cord to be thick, but also increases the price of the optical fiber cord because the expensive tensile strength fiber is additionally used.

Further, since the outer tube is housed gently, there is a drawback that when the connector is attached to the tip, the treatment of uncoupling tensile strength fibers becomes complicated. In addition, the complicated structure in which the optical fiber core wire, the tensile strength fiber, and the outer tube are divided into three parts also causes an increase in the time and effort required for attaching the connector. The complexity of such an end treatment found in the conventional optical fiber cord causes the complexity of the connector attachment and the complexity of the connector structure, resulting in an increase in the price of the optical fiber cord with a connector.

As described above, the conventional optical fiber cord has a structure in which it is difficult to reduce the diameter. Therefore, in an optical communication device or an optical wiring portion between devices in which a large number of optical fiber cords need to be wired, the optical fiber cord is There was the inconvenience that the space required for accommodating them became complicated. In addition, this structure that is difficult to reduce the diameter raises the inconvenience of raising the price of the cord itself and further raising the cost of the terminal treatment of the cord such as attaching a connector.
An object of the present invention is to solve the problems found in the conventional optical fiber cords described above, and to provide an optical fiber cord structure suitable for reducing the diameter and cost.

[0009]

In order to achieve the above-mentioned object, the optical fiber cord of the present invention has an FRP (fiber-reinforced) outer circumference of an optical fiber wire for communication in which the optical fiber is coated with an ultraviolet curing resin or the like. Plastic). The optical fiber cord of the present invention has an outer diameter of 250 μm to 270 μm, and the outer diameter of the strand coated with an ultraviolet curable resin is 160 μm to 18 μm.
It is preferably 0 μm. Further, it is desirable that the reinforcing fiber of FRP is glass fiber or aramid fiber. Further, it is desirable that the tensile elastic modulus of FRP is 1800 kgf / mm ^{2 to} 14000 kgf / mm ² . The bending rigidity value of the optical fiber cord of the present invention is preferably 0.5 kgf · mm ^{2 to} 2.0 kgf · mm ² .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a diagram showing an example of a cross-sectional structure of the optical fiber cord of the present invention. The periphery of the optical fiber element wire 3 in which the outer circumference of the communication optical fiber 1 is coated with the ultraviolet curable resin 2 is directly covered with the FRP 4 including the reinforcing fiber 6 in the plastic material 5.

Since the optical fiber cord of the present invention has such a dense cross-sectional structure, the reinforcing fiber 6 mixed in the FRP coating 4 has no slack with respect to the optical fiber. Therefore, when tension is applied to the optical fiber cord, the reinforcing fiber bears the tension from the low strain region, and the amount of the reinforcing fiber required to realize the target strain-tension characteristic can be reduced. Further, when the connector is attached to the optical fiber cord of the present invention, the reinforcing fiber is the FR.
Since it is fixed to the P coating, as shown in FIG. 3, the assembly is completed only by fixing the outer covering portion to the connector ferrule 21 with an adhesive.

Further, since the optical fiber cord of the present invention has a dense cross-sectional structure, the need for a filling space for the tensile strength fiber, which is indispensable for the conventional optical fiber cord, is eliminated, and as described above, the tensile strength fiber is used. It has become possible to reduce the amount. Therefore, the optical fiber cord of the present invention has a structure suitable for reducing the diameter, and can be configured to have the same outer diameter (250 μm) as the conventional optical fiber core wire. Even if the diameter is reduced to this outer diameter, it is possible to maintain the tensile strength without any practical problems.

A specific example will be described below. First, in order to match the pitch where the optical fibers are arranged with the pitch of the conventional optical fiber strand, the outer diameter of the optical fiber cord of the present invention is set to 2
It is necessary to set the thickness to 50 μm to 270 μm. 25
If the thickness is smaller than 0 μm, the cross-sectional area of the cord is small, so that the cross-sectional area of the FRP jacket for maintaining sufficient tensile strength cannot be secured. On the other hand, when the thickness exceeds 270 μm, there is a problem that some kind of pitch conversion work or parts are required to match the conventional multi-core tape core wire having a pitch of 250 μm.

Next, the outer diameter of the conventional optical fiber element wire is 250 μm as described above, but the optical fiber cord of the present invention has an outer diameter of 250 μm to 27 with the FRP jacket.
Since it is 0 μm, the outer diameter of the optical fiber is 250 μm.
Need to be smaller. In order to apply an FRP jacket capable of ensuring a sufficient tensile strength for practical use, the outer diameter of the optical fiber element wire must be 160 μm to 180 μm. If the outer diameter of the optical fiber element wire is smaller than 160 μm, the coating is thin, so that the optical fiber element wire is easily damaged and the probability of breakage during handling of the optical fiber element wire increases, which is not practical. Further, if it exceeds 180 μm, a sufficient thickness of the FRP jacket cannot be secured.

Next, a specific first embodiment will be described. In this embodiment, glass fibers are used as the reinforcing fibers of the FRP jacket. Young's modulus of glass fiber (tensile modulus)
Is a high-strength glass fiber called T glass, about 8600kgf / mm
² FIG. 4 shows the cross-sectional structure of this optical fiber cord. In the figure, 7 is a glass fiber. Here, the outer diameter of the optical fiber element wire is 160 μm, and the outer diameter of the FRP jacket is 250 μm.
m. The glass fiber content of the FRP jacket is usually about 40 to 70%, which is easy to manufacture. Here, it is assumed that the volume content of the glass fiber is 50%.

The cross-sectional area of the glass fiber is 0.0145 mm in this case.
² The breakage of the optical fiber increases sharply with elongation strain of 4 to 5%. The breakage of the optical fiber caused by the elongation strain of about 2% is a low value that causes no practical problem if the strain application time is short (up to about 100 seconds).
It is calculated to be 1/4000 or less per m.

When the tension which gives the optical fiber cord of the present invention an elongation strain of 2% is calculated, it is about 4.3 kgf. This estimate does not include the effects of the FRP plastic material, the UV-curable resin of the optical fiber strand, and the like. The tensile strength of the optical fiber itself is calculated by adding a Young's modulus of 7200 kgf / mm ² and an outer diameter of 125 μm. The burden on the optical fiber is 1.8 kgf and the burden on the FRP reinforcing fiber is 2.5 kgf. Since it is unthinkable to apply a tension of more than 3 kgf to the optical fiber cord in normal wiring work, a tensile strength that does not pose a practical problem has been realized.

Next, a second embodiment will be described. In this example, aramid fiber is used as the reinforcing fiber of the FRP jacket. Aramid fiber is a fiber commonly known as Kevlar. When Kevlar is used as a reinforcing fiber for FRP, the fiber volume content of FRP is also 40 to 70%.
Is a range that is easy to manufacture. Here, it is set to 50%. The cross-sectional structure of the optical fiber cord in this case is shown in FIG. In the figure, 8 is an aramid fiber.

Here, the outer diameter of the optical fiber is 180
μm, and the outer diameter of the FRP jacket is 255 μm. The tensile elastic modulus of Kevlar is about 13000 kgf / mm ² . When the cross-sectional area of the Kevlar is 0.0128 mm ² , the tensile strength of the Kevlar at an elongation strain of 2% is about 3.3 kgf. Therefore, combined with the tensile strength of the optical fiber itself of 1.8 kgf, the tensile strength of the cord is about 5.1 kgf. As described above, even if the aramid fiber is used, it is possible to obtain an optical fiber cord having a practical tensile strength and having a matching outer diameter with a conventional optical fiber element wire.

As described above, when the outer diameter of the optical fiber cord of the present invention matches that of the conventional optical fiber strand, the multi-core tape cord in which the optical fiber cords of the present invention are arranged side by side and the conventional tape core cord are combined. Can be connected very easily. For example, in the fusion splicing, the optical fiber cord of the present invention can be spliced by the same work as that of the conventional tape core wire simply by removing the coating. Even in connector connection, it can be incorporated into a conventional multi-fiber connector ferrule without changing the arrangement pitch of optical fibers.

It is feared that if the FRP mixed with the reinforcing fiber is coated on the outer circumference, the optical fiber cord becomes hard due to its high tensile elastic modulus and the operability becomes difficult, but the outer diameter is 250 μm to 270 μm. For example, the bending rigidity is in a range that poses no practical problems. The bending rigidity value of one optical fiber having a diameter of 125 μm is 0.086 kgf · mm ² . The bending rigidity value of the optical fiber cord using the glass fiber reinforced FRP is 0.78 kgf · mm ² , and the value using Kevlar is 1.11 kgf · mm ² . 0.5 to 2.0 in practice
About kgf · mm ² is suitable for handling. The bending stiffness values of these fiber optic cords are within this range.

The tensile elastic modulus of FRP is almost determined by the tensile elastic modulus of the reinforcing fiber to be mixed and its volume content. FR
This is because the tensile elastic modulus of the plastic (polymer resin) corresponding to the base portion of P is negligibly small as compared with the reinforcing fiber. In the above-mentioned embodiment, the example in which the glass fiber and the aramid fiber are used as the reinforcing fiber has been explained.
The optimum tensile elastic modulus of the jacket FRP for forming an optical fiber cord of m to 270 μm does not depend on the type of the mixed fiber, and the tensile strength as the cord (here, it is evaluated by the tension value giving 2% elongation strain) Existing) and the bending rigidity to ensure the ease of handling of the cord.

The lower limit of the tensile elastic modulus of FRP is 1800 kgf / mm ²
It is. This value is the lower limit of the bending rigidity value of 0.5 k when the FRP coating thickness is thickest, that is, when the outer diameter of the optical fiber is 160 μm and the outer diameter of the FRP is 270 μm.
Determined by the constraints from gf · mm ² . Bending stiffness value is 0.5 kgf
・ If it is less than mm ² , the optical fiber is too soft and bends easily. When an optical fiber is bent with a small radius and is distorted, it is likely to be broken. Therefore, an optical fiber cord having a bending rigidity value smaller than this lower limit becomes fragile and becomes impractical. Incidentally, the tension that gives 2% elongation strain at this time is 3.12 kgf, which satisfies the practical tension value of 3 kgf.

On the other hand, the upper limit of the tensile elastic modulus of FRP is 14000k.
It is gf / mm ² . This value is the condition when the FRP coating thickness is the thinnest, that is, the outer diameter of the optical fiber wire is 180 μm,
1. Upper limit of bending rigidity value when outer diameter is 250 μm
It is decided by the constraint from 0 kgf · mm ² . The tension that gives 2% elongation strain at this time is 8.41 kgf. When the bending rigidity value is higher than 2.0 kgf · mm ² , the optical fiber cord is hard and difficult to bend, and it becomes difficult to bend or store the cord in the optical wiring.

Therefore, the tensile elastic modulus of FRP has an upper limit in practical use. However, in order to construct this FRP having a tensile elastic modulus of 14000 kgf / mm ² , for example, the volume content of fiber should be 5
If it is 0%, the tensile modulus of elasticity of the reinforcing fiber needs to be 28000 kgf / mm ² . However, even with stainless steel wire or steel wire, which is a material with extremely high tensile modulus,
It is 000 kgf / mm ² , and in reality, it is difficult to realize an FRP having a tensile elastic modulus of 14000 kgf / mm ² .

Even if the steel wire has a high tensile modulus, its breaking strength is lower than that of glass fiber or aramid fiber, so it cannot be used as a reinforcing fiber of an optical fiber cord. This is because the elastic limit of steel wire is as low as 0.2% and it cannot withstand elongation of 2%. The same is true for carbon fiber. Carbon fiber has a tensile modulus of 13700 kgf / mm ²
Although it is relatively high, the breaking elongation is low at 1.5%.

[0027]

As described above, since the optical fiber cord of the present invention has a dense structure, it has an excellent advantage that it is suitable for thinning. Since the optical fiber cord of the present invention has a structure capable of ensuring a sufficient tensile strength for practical use even with a thin outer diameter close to 250 μm in which the pitch can be aligned with the conventional optical fiber element, the optical fiber cord of the present invention can be used as a conventional optical fiber element. If a multi-core tape cord is made by laying out side by side like a wire, it can be easily connected to a conventional multi-core tape core wire. Also, because the reinforcing fibers are fixed in the outer jacket,
Since there is no slack in the reinforcing fiber, and no extra fiber that allows for slack is required, not only can the diameter be reduced, but also the cost can be reduced. Further, when the connector is attached, since the reinforcing fiber is fixed to the outer cover, the connector can be assembled only by fixing the outer cover portion with the adhesive in the hole of the ferrule, and the connector assembling can be greatly simplified.

[Brief description of drawings]

FIG. 1 is a view showing a cross section of a conventional optical fiber cord.

FIG. 2 is a diagram showing a cross section of an optical fiber cord of the present invention.

FIG. 3 is a diagram illustrating a connection between an optical fiber cord and a connector ferrule.

FIG. 4 is a diagram showing a cross section of a first embodiment of the optical fiber cord of the present invention.

FIG. 5 is a diagram showing a cross section of a second embodiment of the optical fiber cord of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber for communication 2 Optical fiber element wire sheath such as UV curable resin 3 Optical fiber element wire 4 FRP 5 Plastic material 6 Reinforcing fiber 7 Glass fiber 8 Aramid fiber 11 Optical fiber core wire 12 Tensile strength fiber 13 Pipe such as PVC or Tube 21 connector ferrule

Claims (7)

[Claims] 1. An FRP is provided around the outer circumference of a communication optical fiber element wire in which an optical fiber is coated with an ultraviolet curing resin or the like.
An optical fiber cord coated with (fiber reinforced plastic). 2. The optical fiber cord according to claim 1, wherein the outer diameter is 250 μm to 270 μm. 3. The outer diameter of a wire made by coating an optical fiber with an ultraviolet curable resin or the like has an outer diameter of 160 μm to 180 μm.
The optical fiber cord according to claim 2, wherein 4. The optical fiber cord according to claim 3, wherein the reinforcing fiber of FRP is glass fiber. 5. The optical fiber cord according to claim 3, wherein the FRP reinforcing fibers are aramid fibers. 6. The tensile elastic modulus of FRP is 1800 kgf / mm ²
4. The optical fiber cord according to claim 3, wherein the optical fiber cord has a weight of 1 to 14000 kgf / mm ² . 7. A flexural rigidity value of 0.5 kgf · mm ^{2 to} 2.
The optical fiber cord according to claim 3, wherein the optical fiber cord has a weight of 0 kgf · mm ² .